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PubMed1997

An NADPH:FAD oxidoreductase from the valanimycin producer, Streptomyces viridifaciens. Cloning, analysis, and overexpression.

The valanimycin producer Streptomyces viridifaciens contains a two-component enzyme system that catalyzes the oxidation of isobutylamine to isobutylhydroxylamine. One component of this enzyme system is isobutylamine hydroxylase, and the other component is a flavin reductase. The gene (vlmR) encoding the flavin reductase required by isobutylamine hydroxylase has been cloned from S. viridifaciens by chromosome walking. The gene codes for a protein of 194 amino acids with a calculated mass of 21,265 Da and a calculated pI of 10.2. Overexpression of the vlmR gene in Escherichia coli as an N-terminal His-tag derivative yielded a soluble protein that was purified to homogeneity. Removal of the N-terminal His-tag from the overexpressed protein by thrombin cleavage also produced a soluble protein. Both forms of the protein exhibited a high degree of flavin reductase activity, and the thrombin-cleaved form functioned in combination with isobutylamine hydroxylase to catalyze the conversion of isobutylamine to isobutylhydroxylamine. Kinetic data indicate that the overexpressed protein utilizes FAD and NADPH in preference to FMN, riboflavin, and NADH. The deduced amino acid sequence of the VlmR protein exhibited similarity to several other flavin reductases that may constitute a new family of flavin reductases.

Amino Acid Sequence↗
PubMed1997

Purification and characterization of 2-hydroxybiphenyl 3-monooxygenase, a novel NADH-dependent, FAD-containing aromatic hydroxylase from Pseudomonas azelaica HBP1.

2-Hydroxybiphenyl 3-monooxygenase (HbpA), the first enzyme of 2-hydroxybiphenyl degradation in Pseudomonas azelaica HBP1, was purified 26-fold with a yield of 8% from strain HBP1 grown on 2-hydroxybiphenyl. The enzyme was also purified from a recombinant of Escherichia coli JM109, which efficiently expressed the hbpA gene. Computer densitometry of scanned slab gels revealed a purity of over 99% for both enzyme preparations. Gel filtration, subunit cross-linking, and SDS-polyacrylamide gel electrophoresis showed that the enzyme was a homotetramer with a molecular mass of 256 kDa. Each subunit had a molecular mass of 60 kDa containing one molecule of noncovalently bound FAD. The monooxygenase had a pI of 6.3. It catalyzed the NADH-dependent ortho-hydroxylation of 2-hydroxybiphenyl to 2,3-dihydroxybiphenyl. Molecular oxygen was the source of the additional oxygen of the product. The enzyme hydroxylated various phenols with a hydrophobic side chain adjacent to the hydroxy group. All substrates effected partial uncoupling of NADH oxidation from hydroxylation with the concomitant formation of hydrogen peroxide. 2,3-Dihydroxybiphenyl, the product of the reaction with 2-hydroxybiphenyl, was a non-substrate effector that strongly facilitated NADH oxidation and hydrogen peroxide formation without being hydroxylated and also was an inhibitor. The apparent Km values (30 degrees C, pH 7.5) were 2.8 microM for 2-hydroxybiphenyl, 26.8 microM for NADH, and 29.2 microM for oxygen. The enzyme was inactivated by p-hydroxymercuribenzoate, a cysteine-blocking reagent. In the presence of 2-hydroxybiphenyl, the enzyme was partly protected against the inactivation, which was reversed by the addition of an excess of dithiothreitol. The NH2-terminal amino acid sequence of the enzyme contained the consensus sequence GXGXXG, indicative of the betaalphabeta-fold of the flavin binding site and shared homologies with that of phenol 2-hydroxylase from Pseudomonas strain EST1001 as well as with that of 2,4-dichlorophenol 6-hydroxylase from Ralstonia eutropha.

Amino Acid Sequence↗
PubMed1990

Women and weight: fad and fiction.

In this article, I argue that women's concern with body weight is a "fad," when taken in an historical context, and is limited to Western societies. I have presented evidence that the following aspects of weight are myths rather than reality: (a) There are objective definitions of obesity; (b) obesity is prevalent among women; (c) obese people take in more calories than the nonobese; (d) dieting is an effective way to reduce weight; and (e) obesity is related to poor physical health.

Attitude to Health↗
PubMed1991

The latest fads to increase muscle mass and energy. A look at what some athletes are using.

How different fads get started in different parts of the country defies rational explanation. This holds true in the world of athletic competition. In one locale athletes may be taking ginseng to promote strength, while in another they may be taking antioxidants to recover quickly after exertion. As Dr Woolley explains, some of the substances used do have the desired effects, some appear to have little or no effect, and some have dangerous effects.

Adolescent↗
PubMed1997

Nucleotide sequence of cDNA fragments coding for the FAD-,glycerophosphate- and calcium-binding domains of human islet mitochondrial glycerophosphate dehydrogenase.

The cDNA fragments coding for the FAD-, glycerophosphate- and calcium-binding domains of mitochondrial glycerophosphate dehydrogenase (mGDH) were synthetized using RNA extracted from freshly isolated pancreatic islets of a normal subject and two-non-insulin-dependent diabetic patients. Single strand conformation polymorphism analysis of the PCR products yielded the same mobility as control cDNA probes. Likewise, the nucleotide sequence and corresponding amino acid sequence were identical to the normal gene bank sequence. These findings argue against the presence, in pancreatic islets, of an mGDH isoform distinct from that previously characterized in extrapancreatic organs.

Aged↗
PubMed2001

The covalent FAD of monoamine oxidase: structural and functional role and mechanism of the flavinylation reaction.

The family of flavoenzymes in which the flavin coenzyme redox cofactor is covalently attached to the protein through an amino acid side chain is covered in this review. Flavin-protein covalent linkages have been shown to exist through each of five known linkages: (a) 8alpha-N(3)-histidyl, (b) 8alpha-N(1)-histidyl, (c) 8alpha-S-cysteinyl, (d) 8alpha-O-tyrosyl, or (e) 6-S-cysteinyl with the flavin existing at either the flavin mononucleotide or flavin adenine dinucleotide (FAD) levels. This class of enzymes is widely distributed in diverse biological systems and catalyzes a variety of enzymatic reactions. Current knowledge on the mechanism of covalent flavin attachment is discussed based on studies on the 8alpha-S-cysteinylFAD of monoamine oxidases A and B, as well as studies on other flavoenzymes. The evidence supports an autocatalytic quinone-methide mechanism of protein flavinylation. Proposals to explain the structural and mechanistic advantages of a covalent flavin linkage in flavoenzymes are presented. It is concluded that multiple factors are involved and include: (a) stabilization of the apoenzyme structure, (b) steric alignment of the cofactor in the active site to facilitate catalysis, and (c) modulation of the redox potential of the covalent flavin through electronic effects of 8alpha-substitution.

Benzoquinones↗
PubMed2002

Expression of SOx-2, a member of the FAD-dependent sulfhydryl oxidase/quiescin Q6 gene family, in rat brain.

Sulfhydryl oxidases belonging to the FAD-dependent sulfhydryl oxidase/quiescin Q6 family were previously reported in rat peripheral organs but they were not detected in brain. In the present study, by using reverse transcription-polymerase chain reaction and northern blot analysis, we clearly show an ubiquitous expression of the gene in brain; moreover, while only one transcript was present in peripheral organs, at least two transcripts were detected in brain, suggesting a tissue-specific splicing of its mRNA. The shorter one, likely corresponding to the mRNA identified from rat seminal vesicles, was highly expressed in diencephalon and telencephalon. The finding of gene expression in brain is relevant, since its dysregulation could lead to oxidative stress, a causative factor in the pathogenesis of neurodegenerative diseases.

Animals↗
PubMed1993

Injuries sustained during flipping--a new fad activity.

This article describes a small series of injuries resulting from a new fad activity among children in Baltimore. "Flipping" involves jumping from an elevated surface and executing an aerial flip, with the intent to land upright. Because this activity takes place frequently on hard surfaces such as concrete, injuries often result. The spectrum of injuries is described and categorized, and injuries are compared with those received during similar activities, such as break dancing or skateboarding, and with playground injuries. Pediatricians and emergency physicians should be aware of the potential for injury in this activity.

Athletic Injuries↗
PubMed1995

The choice of reducing substrate is altered by replacement of an alanine by a proline in the FAD domain of a bispecific NAD(P)H-nitrate reductase from birch.

Differences in the amino acid sequence between the bispecific NAD(P)H-nitrate reductase of birch (Betula pendula Roth) and the monospecific NADH-nitrate reductases of a variety of other higher plants have been found at the dinucleotide-binding site in the FAD domain. To pinpoint amino acid residues that determine the choice of reducing substrate, we introduced mutations into the cDNA coding for birch nitrate reductase. These mutations were aimed at replacing certain amino acids of the NAD(P)H-binding site by conserved amino acids located at identical positions in NADH-monospecific enzymes. The mutated cDNAs were integrated into the genome of tobacco by Agrobacterium-mediated transformation. Transgenic tobacco (Nicotiana tabacum) plants were grown on a medium containing ammonium as the sole nitrogen source to keep endogenous tobacco nitrate reductase activity low. Whereas some of the mutated enzymes showed a slight preference for NADPH, as does the nonmutated birch enzyme, the activity of some others greatly depended on the availability of NADH and was low with NADPH alone. Comparison of the mutations reveals that replacement of a single amino acid in the birch sequence (alanine871 by proline) is critical for the use of reducing substrate.

Alanine↗
PubMed2002

Crystallization of the FAD-independent acetolactate synthase of Klebsiella pneumoniae.

Leucine and valine are formed in a common pathway from pyruvate in which the first intermediate is 2-acetolactate. In some bacteria, this compound also has a catabolic fate as the starting point for the butanediol fermentation. The enzyme (EC 4.1.3.18) that forms 2-acetolactate is known as either acetohydroxyacid synthase (AHAS) or acetolactate synthase (ALS), with the latter name preferred for the catabolic enzyme. A significant difference between AHAS and ALS is that the former requires FAD for catalytic activity, although the reason for this requirement is not well understood. Both enzymes require the cofactor thiamine diphosphate. Here, the crystallization and preliminary X-ray diffraction analysis of the Klebsiella pneumoniae ALS is reported. Data to 2.6 A resolution have been collected at 100 K using a rotating-anode generator and an R-AXIS IV++ detector. Crystals have unit-cell parameters a = 137.4, b = 143.9, c = 134.4 A, alpha = 90, beta = 108.4, gamma = 90 degrees and belong to space group C2. Preliminary analysis indicates that there are four monomers located in each asymmetric unit.

Acetolactate Synthase↗
PubMed2006

The purification, crystallization and preliminary structural characterization of FAD-dependent monooxygenase PhzS, a phenazine-modifying enzyme from Pseudomonas aeruginosa.

The blue chloroform-soluble bacterial metabolite pyocyanin (1-hydroxy-5-methyl-phenazine) contributes to the survival and virulence of Pseudomonas aeruginosa, an important Gram-negative opportunistic pathogen of humans and animals. Little is known about the two enzymes, designated PhzM and PhzS, that function in the synthesis of pyocyanin from phenazine-1-carboxylic acid. In this study, the FAD-dependent monooxygenase PhzS was purified and crystallized from lithium sulfate/ammonium sulfate/sodium citrate pH 5.5. Native crystals belong to space group C2, with unit-cell parameters a = 144.2, b = 96.2, c = 71.7 A, alpha = gamma = 90, beta = 110.5 degrees. They contain two monomers of PhzS in the asymmetric unit and diffract to a resolution of 2.4 A. Seleno-L-methionine-labelled PhzS also crystallizes in space group C2, but the unit-cell parameters change to a = 70.6, b = 76.2, c = 80.2 A, alpha = gamma = 90, beta = 110.5 degrees and the diffraction limit is 2.7 A.

Bacterial Proteins↗
PubMed1991

Purification and characterisation of 3-hydroxyphenylacetate 6-hydroxylase: a novel FAD-dependent monooxygenase from a Flavobacterium species.

3-Hydroxyphenylacetate 6-hydroxylase was purified 70-fold from a Flavobacterium sp. grown upon phenylacetic acid as its sole carbon and energy source. The presence of FAD and dithiothreitol during purification is essential for high recovery of active enzyme. SDS/PAGE of purified enzyme reveals a single band with a minimum molecular mass of 63 kDa. Analytical gel-filtration, sedimentation-equilibrium and sedimentation-velocity experiments indicate that the purified enzyme exists in solution mainly as a dimer, containing 1 molecule non-covalently bound FAD/subunit. 3-Hydroxyphenylacetate 6-hydroxylase utilizes NADH and NADPH as external electron donors with similar efficiency. The enzyme shows a narrow substrate specificity. Only the primary substrate 3-hydroxyphenylacetate is hydroxylated efficiently, yielding 2,5-dihydroxyphenylacetate as a product. During turnover, the substrate analogues 3,4-dihydroxyphenylacetate and 4-hydroxyphenylacetate are partially hydroxylated, exclusively at the 6' (2') position. The physiological product 2,5-dihydroxyphenylacetate acts as an effector, strongly stimulating NAD(P)H oxidation. The activity of 3-hydroxyphenylacetate 6-hydroxylase is severely inhibited by chloride ions, competitive to the aromatic substrate. In the native state of enzyme, two sulfhydryl groups are accessible to 5,5'-dithiobis(2-nitrobenzoate). Titration with stoichiometric amounts of either 5,5'-dithiobis(2-nitrobenzoate) or mercurial reagents completely blocks enzyme activity. Inactivation by cysteine reagents is inhibited by the substrate 3-hydroxyphenylacetate. The original activity is fully restored by treatment of the modified enzyme with dithiothreitol. The N-terminal amino acid sequence of the enzyme lacks the consensus sequence GXGXXG, found at the N-termini of all flavin-dependent external monooxygenases sequenced so far. The amino acid composition of 3-hydroxyphenylacetate 6-hydroxylase is also presented.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of vanillyl-alcohol oxidase from Penicillium simplicissimum. A novel aromatic alcohol oxidase containing covalently bound FAD.

Vanillyl-alcohol oxidase was purified 32-fold from Penicillium simplicissimum, grown on veratryl alcohol as its sole source of carbon and energy. SDS/PAGE of the purified enzyme reveals a single fluorescent band of 65 kDa. Gel filtration and sedimentation-velocity experiments indicate that the purified enzyme exists in solution as an octamer, containing 1 molecule flavin/subunit. The covalently bound prosthetic group of the enzyme was identified as 8 alpha-(N3-histidyl)-FAD from pH-dependent fluorescence quenching (pKa = 4.85) and no decrease in fluorescence upon reduction with sodium borohydride. The enzyme shows a narrow substrate specificity, only vanillyl alcohol and 4-hydroxybenzyl alcohol are substrates for the enzyme. Cinnamyl alcohol is a strong competitive inhibitor of vanillyl-alcohol oxidation. The visible absorption spectrum of the oxidized enzyme shows maxima at 354 nm and 439 nm, and shoulders at 370, 417 and 461 nm. Under anaerobic conditions, the enzyme is easily reduced by vanillyl alcohol to the two-electron reduced form. Upon mixing with air, rapid reoxidation of the flavin occurs. Both with dithionite reduction and photoreduction in the presence of EDTA and 5-deazaflavin the red semiquinone flavin radical is transiently stabilized. Opposite to most flavoprotein oxidases, vanillyl-alcohol oxidase does not form a flavin N5-sulfite adduct. Photoreduction of the enzyme in the presence of the competitive inhibitor cinnamyl alcohol gives rise to a complete, irreversible bleaching of the flavin spectrum.

Alcohol Oxidoreductases↗
PubMed1994

F420H2: quinone oxidoreductase from Archaeoglobus fulgidus. Characterization of a membrane-bound multisubunit complex containing FAD and iron-sulfur clusters.

Archaeoglobus fulgidus, a hyperthermophilic sulfate-reducing archaeon, was found to contain a membrane-bound F420H2: quinone oxidoreductase complex presumed to be involved in energy conservation during growth on lactate plus sulfate. After solubilization with dodecyl-beta-D-maltoside the complex was purified 32-fold with a yield of 24%. Using both gel filtration and native PAGE, an apparent molecular mass of approximately 270 kDa was determined. SDS/PAGE revealed the presence of at least seven polypeptides with apparent molecular masses 56, 45, 41, 39, 37, 33, and 32 kDa. The purified complex contained 1.6 mol FAD, 9 mol non-heme iron and 7 mol acid-labile sulfur/mol complex. It did not contain cytochromes, which were, however, present in the membrane fraction of A. fulgidus (3 nmol/mg membrane protein). The purified F420H2: quinone oxidoreductase complex catalyzed the reduction of 2,3-dimethyl-1,4-naphthoquinone (apparent Km 190 microM) with reduced coenzyme F420 (apparent Km 50 microM) exhibiting a specific activity of 500 U/mg (apparent Vmax) at pH 8.0 (pH optimum) and 65 degrees C (temperature optimum). 2-Methyl-1,4-naphthoquinone (menadione), 2-hydroxy-1,4-naphthoquinone, 1,4-naphthoquinone, 2,3-dimethoxy-5-methyl-1,4- benzoquinone, and 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (decyl-ubiquinone) were also reduced with F420H2, albeit with lower rates. The physiological electron acceptor of the F420H2: quinone oxidoreductase complex is most likely the menaquinone found in the membrane fraction of A. fulgidus.

Amino Acid Sequence↗
PubMed1995

An essential lysyl residue (Lys208) in the substrate-binding site of porcine FAD-containing monooxygenase.

The substrate (amine)-binding site of porcine FAD-containing monooxygenase (FMO) (EC 1.14.13.8) was examined using pyridoxal 5'-phosphate (pyridoxal-P) to modify lysyl residues. The enzymic activity of the FMO was inhibited competitively by pyridoxal-P. Upon reduction of pyridoxal-P-treated FMO with NaBH4, a new characteristic absorption peak of substituted pyridoxal-P appeared at 325 nm. The amino acid residue compositions of the native and pyridoxal-P-treated FMOs indicated that the lysyl residues were modified by pyridoxal-P. The about 74% inactivation of the enzymic activity on covalent pyridoxal-P treatment of the FMO was nearly completely prevented in the presence of the substrate, N,N-dimethylaniline. The FMO covalently modified with pyridoxal-P in the presence or absence of N,N-dimethylaniline was digested with trypsin treated with tosylphenylalanylchloromethane and the resultant peptide fragments were separated with a reverse-phase high-performance liquid chromatography system; only one peptide was specifically labeled with pyridoxal-P and was detected at 325 nm in the absence of N,N-dimethylaniline. The modified peptide was analyzed and identified as that comprising the amino acid residues 186-208. These results suggest that Lys208 plays an important role in the substrate (amine)-binding site of FMO.

Amino Acid Sequence↗
PubMed2005

Cloning, characterization and expression of escapin, a broadly antimicrobial FAD-containing L-amino acid oxidase from ink of the sea hare Aplysia californica.

A 60 kDa monomeric protein isolated from the defensive purple ink secretion of the sea hare Aplysia californica was cloned and sequenced, and is the first sea hare antimicrobial protein to be functionally expressed in E. coli. Sequence analysis suggested that this protein is a flavin-containing l-amino acid oxidase (LAAO), with one predicted potential glycosylation site, although the glycosylation could not be experimentally confirmed. This protein, which we call ;escapin', has high sequence similarity to several other gastropod proteins. Escapin was verified by NMR, mass spectroscopy and HPLC to have FAD as its flavin cofactor. Escapin's antimicrobial effects, bacteriostasis and bactericidal, were determined using a combination of two assays: (1) incubation of bacteria on solid media followed by assessment of inhibition by direct observation of zones of inhibition or by turbidity measurements; and (2) incubation of bacteria in liquid media followed by counting viable colonies after growing on agar plates. Native escapin inhibited the growth of Gram-positive and Gram-negative bacteria, including marine bacteria (Vibrio harveyii and Staphylococcus aureus) and pathogenic bacteria (Staphylococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa). Escapin also inhibited the growth of yeast and fungi, with different efficacies. Escapin's antimicrobial activity was concentration dependent and did not decrease when stored for more than 5 months at room temperature. Escapin was bacteriostatic and not bactericidal in minimal media (e.g. salt media) with glucose, yeast extract, and a mixture of 20 amino acids each at 50 micromol l(-1), but was bactericidal in media enriched with Tryptone Peptone. Escapin was also strongly bactericidal in media with l-lysine at concentrations as low as 3 mmol l(-1) and slightly bactericidal in 50 mmol l(-1) l-arginine, but not in most other amino acids even at 50 mmol l(-1). Escapin had high oxidase activity (producing hydrogen peroxide) with either l-arginine or l-lysine as a substrate and little to no oxidase activity with other l-amino acids. Hydrogen peroxide alone (without escapin or amino acids) was strongly bacteriostatic but poorly bactericidal, similar in this respect to l-arginine but different from l-lysine in the presence of escapin. Together these results suggest that there are multiple mechanisms to escapin's antimicrobial effects, with bacteriostasis resulting largely or entirely from the effects of hydrogen peroxide produced by escapin's LAAO activity, but bactericidal effects resulting from lysine-dependent mechanisms not directly involving hydrogen peroxide. Recombinant escapin expressed in bacteria was also active against Gram-positive and Gram-negative bacteria, suggesting that glycosylation is not essential for antimicrobial activity.

Amino Acid Sequence↗
PubMed1985

Purification and properties of an FAD-containing NADH oxidase from Mycoplasma capricolum.

From the prokaryotic microorganism Mycoplasma capricolum an FAD-containing NADH oxidase has been purified by preparative FPLC to homogeneity, as judged by polyacrylamide gel electrophoresis. The apparent molecular mass of the enzyme was found to be 72.5 kDa, with an isoelectric point of 5.2, and no detectable subunits. No iron, copper, manganese or molybdenium could be detected. On the basis of a minimum molecular mass of 72.5 kDa a ratio of FAD/protein of 1:1 could be derived. Its amino-acid composition, the light absorption and the fluorescence spectra are presented.

Amino Acids↗
PubMed1988

Cytochrome P-450 and FAD-monooxygenase mediated S- and N-oxygenations.

S- and N-Oxygenations are mostly mediated by either the cytochrome P-450 group of enzymes (haemoproteins), or the FAD-containing monooxygenases (flavoproteins). The nucleophilicity of the heteroatom may be an important determinant of which of these microsomal enzymes is utilised for specific oxygenations. This article describes the approaches that could be used for assessing the relative contribution of these microsomal oxidases to a particular reaction, with reference to studies with N,N-dimethylaniline, diethylsulphide, tetrahydrothiophen and dibenzothiophen.

Animals↗